The door to large commercial freezers, refrigerators and warehouses must be left open or opened many times each day in order to permit the movement of personnel and material handling equipment through the door. Whenever the door is opened or left open, there is an energy loss due to heat transfer between the cold or warm area inside and the ambient conditions outside.
To reduce this energy loss and to provide other advantages, environmental curtains are commonly used to close the opening leading to a controlled environmental zone. An environmental curtain typically includes elongated flexible plastic strips having their upper ends formed into loops and a curtain support extending through the loops. The curtain support is mounted in the doorway to suspend the flexible strips in the doorway in side-by-side overlapping relationship. In this manner, the doorway remains closed, except when personnel or equipment are passing through, and in this event, the strips are only pushed aside to the extent necessary for passage of the personnel or equipment.
Although environmental curtains of this type function very satisfactorily, they are somewhat difficult to install on the curtain support. According to one prior art technique, the upper end of each flexible strip is permanently heat-welded to form a loop through which the curtain support can be extended. One problem with this construction is that the strips are difficult to install because the curtain support must first be detached at one end to allow the loops to be slid over the free end of the curtain support.
Another prior art technique utilizes separate threaded fasteners to form the upper ends of the flexible strips into loops. The fasteners can be removed. However, the use of separate fasteners adds to the cost of installation and requires more time to install the strips than is desirable.
All of these prior art constructions provide loops of very substantial strength for each of the flexible strips. Although strong construction is desirable, it is a distinct disadvantage when the lower end of one of the strips becomes inadvertently attached to a vehicle, such as a forklift truck, moving through the doorway. In this event, the entire strip door, including the curtain support and all of the strips can be pulled down. This is a potential source of injury to personnel and damage to equipment.